I haven't tested itmyself (as I don't really have a need to use a text area) but you've tried changing this:
Code
	if ($config['CUSTOM_FIELD_1']) {
		$CUSTOM_FIELD_1 = "
		{$config['CUSTOM_FIELD_1']}
		<br />
		<input type=\"text\" name=\"CUSTOM_FIELD_1\" value=\"$CUSTOM_FIELD_1\" class=\"form-input\" />
		<br />
		<br />
		";
	}

in scripts/editbasic.inc.php? It seems trivial, I'm just hoping that you tested the correct areas in your search.

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